1. Field of the Invention
This invention relates to control systems for machines and the like of the type having at least one cycle made up of at least two events where one of the events may include at least two subevents and is more particularly concerned with control systems capable of accommodating a plurality of momentarily operable switching devices wherein at least one of the switching devices actuates the machine cycle.
Generally speaking, the control system of the present invention includes a control circuit having programming means, digital circuitry for implementing the programming means and latching the control circuit in various modes of operation, and timing circuitry responsive to the digital circuitry for deriving a selectable timing period for at least one of the events of the cycle; delay timing means for sequentially activating and deactivating the subevents; and gate circuit means for regulating at least another of the events in response to the control circuit.
2. Description of the Prior Art
The present invention represents an improvement upon our copending patent application Ser. No. 807,009 entitled "Control System Utilizing Momentary Switching Devices." U.S. Pat. Nos. 3,767,937 and 3,973,135 assigned to P. R. Mallory & Co. Inc. disclose control systems which include control circuits having timing means and other circuitry for controlling machines and the like having at least one cycle made up of at least one event. Our copending patent application, Ser. No. 807,009 improved upon U.S. Pat. Nos. 3,767,937 and 3,973,135 by introducing the use of momentary switching devices and associated circuitry to latch the control circuit in an operation mode. The present invention is a further improvement upon a control system which includes the capability of accommodating a plurality of momentary switching devices.
Previous control systems have utilized pushbutton switching devices which latch in the on position when pushed or pulled and are then released or latched in the off position in response to a solenoid release. These types of mechanical switching devices are now undesirable in many applications of control systems because of cost, reliability, and esthetics. Accordingly, latching mechanical switching devices are being replaced by momentary switching devices such as keyboard type switches or electronic touch switches as will be recognized by reference to recently issued U.S. Pat. No. 4,001,599. Since momentary switching devices do not latch, other means must be employed to latch the control circuit in various modes of operation; however, many of these latching means also limit the number of momentary switches which may be accommodated by the control circuit.
Generally, the timing means associated with control systems such as those disclosed in U.S. Pat. Nos. 3,767,937 and 3,973,135 have utilized an oscillator circuit in conjunction with a resistance capacitance timing network in order to provide a timing period for at least one event of a cycle of the machine being controlled. Where mechanical switching devices have been used, such timing means have necessitated a means for latching the timing means into a desired timing period. Accordingly, mechanical switching devices having double contacts were usually employed i.e. one contact to latch the control circuit in an operational mode and one contact to select and latch the appropriate resistance capacitance combination for a desired timing period. With the utilization of momentary switching devices to actuate a cycle of the machine, timing means required improvement so that they would not depend upon the latching of a mechanical switching device for the selection of a timing period.
Improvements to timing means have included the use of an oscillator circuit which produces a series of electrical pulses which are in turn counted to derive a timing period for a particular cycle or event of a machine such as those disclosed in U.S. Pat. No. 3,774,056 and 4,001,599; however, in most of the improvements, a timing period is predicated solely upon the number of electrical pulses counted and not upon the frequency of such pulses. Furthermore, many of such improved timing means are limited to specific timing periods once they are assembled.
Generally speaking, therefore, the present invention represents an improvement upon the control systems as disclosed in U.S. Pat. Nos. 3,767,937 and 3,973,135 and a further improvement upon our copending patent application Ser. No. 807,009 wherein the present control system is capable of accommodating a plurality of momentary switching devices and provides a plurality of selectable timing periods which can be easily altered after assembly of the control system.